Coating apparatus for coating a flexible web



Nov. 10, 1970 F. P. KOLESINSKAS 3,539,384

COATING APPARATUS FOR COATING A FLEXIBLE WEB Filed June 30, 1967 PRIORART INVENTOQR. Frank P. Kolesinskus B) ATTORNEY United States Patent3,539,384 COATING APPARATUS FOR COATING A FLEXIBLE WEB Frank P.Kolesinskas, Binghamton, N.Y., assignor to GAF Corporation, New York,N.Y., a corporation of Delaware Filed June 30, 1967, Ser. No. 650,422Int. Cl. B05c 1/12 US. Cl. 117111 1 Claim ABSTRACT OF THE DISCLOSURE Forapplying a uniform coating layer to a web of diazotype film moving athigh speed there is provided a pick-up roller having an annular surfacerotatable in a liquid coating solution, a transfer roller having anannular surface rotatable in spaced relationship with that of thepick-up roller to thereby reverse, split and receive only a portion ofthe coating solution therefrom, and a moving film web the surface ofwhich is spaced from that of the transfer roller, and also only aportion of the solution carried on the surface of the transfer roller.The smoothing return flow due to the splitting of the wet film on thetransfer roller and on the pick-up roller, facilitates the uniformcoating of a film web moving at high speed.

This invention relates to a method and apparatus for coating a flexibleweb and, in particular, for applying a uniform layer of coating solutionto the surface of a continuously moving web of diazo-type film material.

The continuous and rapid increase in the production of diazo-type films,such as microfilm or the like, has stimulated the need for thedevelopment of efficient high speed methods and apparatus which arecapable of applying high quality coating to the film. In essence, thecoating process concerns itself primarily with the uniform applicationof a coating solution to diazo-type films without the necessity ofproviding the so-called solution flowout after application, to the filmsurface. Prior art methods and apparatus, in general, have proventhemselves to be sloW in terms of production output and incapable ofmeeting present day industrial and technical demands.

Among presently used solution coating methods, which are described to beof the high speed production type, are those employing. air knives,gravure and reverse roll solution coating systems. These have proventhemselves to be generally satisfactory when used in connection withcommercial diazo-type film processing installations and systems, but aresubject to some limitations. In particular, these limitations have beenthe relatively complex and expensive apparatuses which are required forthe pneumatic devices employing air doctor blades or knives, and thepoor coating results obtained at higher production speeds when usingprior art devices incorporating gravure or reverse roll systems. Athigher roller speeds, when using gravure or roller devices rotating in atrough containing a coating solution, waves and ridges are formed in thesolution layer on the surfaces of the pick-up rollers. Theseirregularities in the solution thickness are transmitted to the filmpassing adjacent to the pick-up rollers, causing drastic deteriorationsin the quality of the coated film, and at times, making the filmcompletely unusuable. Consequently, it becomes quite evident that theprior art film coating methods and apparatuses are not sufiicientlysuitable when applied to the large quantity, high speed production ofsophisticated film products such as diazotype micro-film.

The novel and improved diazo-type film coating apparatus and methodaccording to the present invention,

Patented Nov. 10, 1970 "ice overcomes the foregoing and otherdisadvantages encountered in the prior art, by providing a coatingapparatus which includes a rotatable pick-up roller adapted to rotate athigh speeds in a trough containing a diazo coating solution, a transferroller rotatable in a predetermined relationship with the pick-up rollerand which receives a portion of the coating solution from the latter,and a continuously moving web of film material adapted to receive thecoating solution from the transfer roller. A primary advantage of theuse of the transfer roller intermediate to the pick-up roller and thefilm web is that it has a smoothing eifect on the coating solutionremoved from the trough by the pick-up roller. In effect, a portion ofthe coating solution picked up by the pick-up roller is transferred tothe surface of the transfer roller, while the remainder of the solutionpasses between the pick-up and transfer rollers and returns to thetrough. The portion of the coating solution transferred to the transferroller is then conveyed by the latter about an angular displacement ofat least This will allow. the coating solution on the surface of thetransfer roller to smooth itself under the action of gravity.Subsequently, the coating solution is deposited on the surface of a webof film material being conveyed past the transfer roller, and produces asmooth, high quality coating of the solution on the film. Theutilization of intermediate transfer rollers will facilitate the highspeed operation of reverse roll coating apparatuses, allowing the filmto be satisfactorily coated at film speeds in excess of I00 feet/minute.

Accordingly, it is a primary object of the present invention to providean improved and novel film coating apparatus facilitating the highspeed, quality coating of diazo-type film Webs.

Another object of the present invention is to provide a novel filmcoating apparatus utilizing a rotatable pickup roller adapted to receivecoating solution from a trough, a rotatable transfer roller cooperativewith the pick-up roller so as to receive a portion of the coatingsolution therefrom, and a continuously moving web of film material whichis coated with the coating solution carried by the transfer roller.

A further object of the present invention is to provide a novel methodof coating a moving web of diazo-type film through the use of a reverseroller coating apparatus.

A more specific object of the present invention is to provide a novelmethod of applying a coating solution to the usrface of a moving web ofdiazo-type film by means of a transfer roller which receives the coatingsolution from a cooperative rotatable pick-up roller.

These and other objects and many of the attendant advantages of thisinvention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings in which:

FIG. 1 is a diagrammatic view of a prior art coating apparatus;

FIG. 2 is a diagrammatic view of a preferred embodiment of a diazo-typefilm coating apparatus according to the present invention;

FIG. 3 is a second embodiment of a coating apparatus according to thepresent invention;

FIG. 4 is a third embodiment of a coating apparatus according to thepresent invention;

FIG. 5 is a fourth embodiment of a coating apparatus according to thepresent invention; and

FIG. 6 is a fifth embodiment of a coating apparatus according to thepresent invention.

Referring now to the drawings, wherein like reference charactersdesignate like or corresponding parts through out the several views,FIG. 1 illustrates a prior art coating apparatus of the so-called tworoll reverse roll bear type. A pick-up or applicator roller 1 is adaptedto rotate in a trough 2 containing a quantity ofdiazotype film coatingor developer solution. Applicator roller 1 picks up a portion of thecoating solution on its surface, and conveys the solution into contactwith a moving web of film material 3. Film material 3 is conveyed pastapplicator roller 1 by means of a conveyor roller 4 which rotates in thesame direction as applicator roller 1. Consequently, the solution onapplicator roller 1 is transferred to the surface of the film material 3in a relatively smooth and uniform manner. Although the aforedescribedcoating apparatus is satisfactory when utilized at relatively low filmweb and applicator roller speeds, diificulties have been encountered athigher speeds in excess of 23 linear feet/minute. When the applicatorroller 1 is rotated at higher speeds, coating solution waves aregenerated in the trough, which result in an uneven application ofcoating solution on the surface of roller 1. Since the film web material3 receives the coating solution directly from roller 1, theirregularities and waves in the thickness of the solution aretransferred to the web. This, of course, res lts the formation of a lowquality film coating wh ch is unacceptable in an industry requiring ahigh standard of coating quality.

The diazo-type film coating apparatus 4 according to the presentinvention, as shown in FIG. 2, includes a pick-up roller 5 rotating intrough 2 which contains a quantity of the developer or film coatingsolution. A transfer roller 6 is positioned in closely spacedrelationship with pick-up roller 5, so as to provide a controllable gap'7 between the rollers. Transfer roller 6 is adapted to the rotated inthe same direction as the direction of rotation of pick-up roller 5.

Film web 3 is entrained about a conveyor or backing roller 8, and isarranged to move past the surface of transfer roller 6 in closely spacedrelationship, forming a gap 9 with transfer roller 6. Backing roller 8is rotated in the same direction as the direction of rotation oftransfer roller 6.

During operation, pick-up roller 5 is rotated in the trough 2 atrelatively high speeds, in excess of to 30 linear feet/minute, pickingup a quantity of developer or coating solution on its surface. At thesehigh speeds, waves are generated in the solution in the trough 2, whichin turn cause the solution on the surface of the pick-up roller to beuneven in thickness, and interspersed with waves and ridges. When thesolution on pick-up roller 5 reaches the nip or gap 7 between the latterroller and transfer roller 6, a portion of the solution deposited on thesurface of the transfer roller, while the remainder of the solutionpasses through the gap 7 and is returned to the trough 2 along the backportion of pick-up roller 5. The splitting or dividing of the coatingsolution between pick-up roller 5 and transfer roller 6 will tend toreduce the irregularities and waves in the coating solution transferredto the surface of transfer roller 6.

Concurrently, the solution on the surface of transfer roller 6 isrotated toward gap 9 between film web 3 and transfer roller 6, and isdeposited onto the surface of the film web in a manner well known in theart. Inasmuch as the coating solution on the surface of the transferroller 6 is rotated through an angular displacement of approximately270, it will tend to level itself off under the influence of gravityduring rotation. In effect, this will assure that a smooth coating ofthe solution will be deposited uniformly over the contacted surface offilm web 3.

In order to avoid an excess of coating solution being deposited on thetransfer roller 6 and film web 3, the transfer roller 6 is rotated at agreater linear peripheral speed than that of pick-up roller 5.Similarly, film web 3 may be moved at a greater linear speed tran theperipheral surface speed of transfer roller 6. This will permit thecoating solution which is removed from trough 2 by pick-up roller 5 tobe spread over a larger surface in an equal and uniformly distributedthickness. Typical speed ratios, which have been proven to besatisfactory in operation, are rotation of the pickup roller 5 at alinear surface velocity of 4 5 feet/minute, and the film web 3 at alinear velocity of 60 feet/minute. Essentially, the speed ratio betweenthe transfer roller 6 and pick-up roller 5 may be in the order of 3:2,while similar ratios may be maintained between the film web 3 andtransfer roller 6 depending upon the desired coating solution thicknesson the film surface. In present diazo-type coatings, the above mentionedspeed ratios, in conjunction with proper adjustments of roller gaps 7and 9 produce final smooth film coatings of 2.5 cc./ square foot.

It is to be noted that the above mentioned speed ratios are given by wayof example only, and that other speeds and combinations thereof may beemployed for different types of developer and diazo-type coatingsolutions as required by the particular applications.

Referring now to the embodiments illustrated in FIGS. 3 to 6 of thedrawings, these are in many essential respects quite similar to theembodiment of FIG. 2. Thus, FIGS. 3, 4 and 5 show the apparatuseswherein the backing rollers 8 are positioned at an angle of from thepick-up rollers 5 when measured about the circumference of the transferrollers 6. However, in the embodiment of FIG. 3, the film web 3 which isentrained about backing roller 8 is conveyed at an angle relative toroller gap 9, whereas in FIG. 4 the film web extends in verticalparallel directions from the backing roller. In the embodiment of FIG. 5the web diverges from backing roller 8. Aside from these constructionaldistinctions, which may be each particularly suitable for specificcoating applications, the principle of operation is quite analogous tothat of the apparatus emboided in FIG. 2 of the drawings.

Respecting the embodiment of the apparatus shown in FIG. 6, this isessentially similar to that of FIG. 2, in that it allows the coatin'solution conveyed by the transfer roller 6 to rotate through an angulardisplacement of 270. In this embodiment, however, the film web is movedparallel to the surface of transfer roller 6, and is directed overdirection-changing idler rollers 10.

In addition to the foregoing, the diameters of pick-up roller 5,transfer roller 6 and backing roller 8 may be varied and used indifferent combinations in order to obtain the desired coating thicknessand consistency.

In essence, the foregoing achieves the basic objective of the invention,by splitting the solution between the pick-up roller and transferroller, and the subsequent deposit of the solution onto the film websurface; minimizes any disturbances occurring to the liquid meniscus inthe solution trough 2; and accurately meters the solution over the websurface at relatively high speeds previ ously unattainable in the priorart.

It should also be understood that the foregoing relates to only apreferred embodiment of the invention, and that it is intended to coverall changes and modifications of the example of the invention hereinchosen for the purposes of the disclosure, which do not constitutedepartures from the spirit and scope of the invention.

What is claimed is:

1. A method of uniformly applying a liquid coating solution to thesurface of a rapidly moving web of film material, comprising:

rotating the annular surface of a pick-up roller in a trough containinga quantity of said liquid coating solution,

split-transferring only a portion of the resulting film of said coatingsolution from the annular surface of said pick-up roller to that of arotatable transfer roller,

conveying said web in the reverse direction in spaced relationship pastthe rotating surface of said transfer roller,

and thereby split-transferring only a portion of the liquid coatingsolution carried by the surface of said transfer roller to the reverselymoving adjacent surface of said web of film material.

References Cited UNITED STATES PATENTS 6 FOREIGN PATENTS 788,939 1/1958Great Britain.

RALPH S. KENDALL, Primary Examiner U.S. Cl. X.R.

